ObjectiveTo determine the contribution of soft-tissue trauma plus hemorrhage, bone fracture and hemorrhage, as well as the contribution of bone fracture, soft-tissue trauma and hemorrhage on host immune function.SubjectsAdult male mice (n = 6/group).DesignProspective, randomized, controlled study.SettingAnimal laboratory at a university-affiliated hospital.InterventionsClosed-bone fracture (right lower leg; external fixation) and/or soft-tissue trauma (2.5-cm midline laparotomy, closed in two layers) were induced before hemorrhagic shock (mean arterial blood pressure of 35 +/- 5 (SEM) mm Hg for 90 mins, followed by fluid resuscitation) in male C3H/HeN mice and the animals were killed at 72 hrs after initiation of the experiment.Measurements and Main ResultsSplenocyte interleukin (IL)-2 and IL-3 release capacity, as well as splenic and peritoneal macrophage IL-1 and IL-6 release capacity were determined. Different traumatic insults, i.e., bone fracture or soft-tissue trauma in conjunction with hemorrhage, produced comparable immune depression. More significant depression of splenocyte IL-2 and IL-3 release capacity as well as macrophage IL-1 and IL-6 release capacity occurred with the combined insult (i.e., bone fracture/soft-tissue injury and hemorrhage) than after bone injury or tissue trauma alone with hemorrhage.ConclusionsThe combination of closed-bone fracture and soft-tissue trauma before hemorrhage leads to even more compromised immunity than either soft-tissue trauma or closed-bone fracture along with hemorrhage. The markedly depressed immune function following bone injury, soft-tissue trauma, and hemorrhagic shock may contribute to the increased susceptibility of severely injured patients to sepsis and the ensuing multiple organ failure in the clinical situation. (Crit Care Med 1998; 26:1372-1378)